Beamforming training in orthogonal frequency division multiple access (ofdma) communication systems

ABSTRACT

A beamforming training packet is transmitted from a first communication device to multiple second communication devices. A trigger frame is generated at the first communication device to trigger an uplink orthogonal frequency division multiple access (OFDMA) transmission of beamforming training feedback from at least some of the multiple second communication devices. After transmission of the beamforming training packet by the first communication device, the trigger frame is transmitted to the at least some of the multiple communication devices. The uplink OFDMA transmission is then received at the first communication device. The uplink OFDMA transmission includes respective beamforming training feedback packets generated based on the beamforming training packet by respective ones of the at least some of the multiple second communication devices. The respective beamforming training feedback packets are simultaneously transmitted by the at least some of the multiple second communication devices.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation of U.S. patent application Ser. No.15/144,543, now U.S. Pat. No. 10,390,328, entitled “Beamforming Trainingin Orthogonal Frequency Division Multiple Access (OFDMA) CommunicationSystems,” filed on May 2, 2016, which is a continuation-in-part of U.S.patent application Ser. No. 14/961,380, now U.S. Pat. No. 10,334,571,entitled “Trigger Frame Format for Orthogonal Frequency DivisionMultiple Access (OFDMA) communication,” filed on Dec. 7, 2015, whichclaims the benefit of U.S. Provisional Patent Application Nos.:62/088,257, entitled “SYNC Design,” filed on Dec. 5, 2014; 62/112,528,entitled “SYNC Design,” filed on Feb. 5, 2015; 62/112,894, entitled“SYNC Design,” filed on Feb. 6, 2015; 62/156,069, entitled “BeamformingFeedback per OFDMA,” filed on May 1, 2015; No. 62/204,164, entitled“SYNC (Trigger Frame) Design,” filed on Aug. 12, 2015; 62/244,283,entitled “OFDMA Beamforming Feedback,” filed on Oct. 21, 2015; and62/255,822, entitled “DL OFDMA with Broadcast RU,” filed on Nov. 16,2015. Additionally, U.S. patent application Ser. No. 15/144,543 claimsthe benefit of U.S. Provisional Patent Application No. 62/156,069,entitled “Beamforming Feedback per OFDMA,” filed on May 1, 2015. All ofthe applications referenced above are hereby incorporated by referenceherein in their entireties.

Additionally, the present application is related to U.S. patentapplication Ser. No. 14/961,635, now U.S. Pat. No. 10,375,679, entitled“Trigger Frame Format for Orthogonal Frequency Division Multiple Access(OFDMA) communication,” filed on Dec. 7, 2015, which is incorporated byreference herein in its entirety.

FIELD OF THE DISCLOSURE

The present disclosure relates generally to communication networks and,more particularly, to wireless local area networks that utilizeorthogonal frequency division multiplexing (OFDM).

BACKGROUND

When operating in an infrastructure mode, wireless local area networks(WLANs) typically include an access point (AP) and one or more clientstations. WLANs have evolved rapidly over the past decade. Developmentof WLAN standards such as the Institute for Electrical and ElectronicsEngineers (IEEE) 802.11a, 802.11b, 802.11g, and 802.11n Standards hasimproved single-user peak data throughput. For example, the IEEE 802.11bStandard specifies a single-user peak throughput of 11 megabits persecond (Mbps), the IEEE 802.11a and 802.11g Standards specify asingle-user peak throughput of 54 Mbps, the IEEE 802.11n Standardspecifies a single-user peak throughput of 600 Mbps, and the IEEE802.11ac Standard specifies a single-user peak throughput in thegigabits per second (Gbps) range. Future standards promise to provideeven greater throughputs, such as throughputs in the tens of Gbps range.

These WLANs operate in either a unicast mode or a multicast mode. In theunicast mode, the AP transmits information to one client station at atime. In the multicast mode, the same information is concurrentlytransmitted to a group of client stations.

SUMMARY

In an embodiment, a method for beamforming training in a wirelesscommunication network includes transmitting, from a first communicationdevice, a beamforming training packet to multiple second communicationdevices. The method also includes generating, at the first communicationdevice, a trigger frame to trigger an uplink orthogonal frequencydivision multiple access (OFDMA) transmission of beamforming trainingfeedback from at least some of the multiple second communicationdevices. The method further includes transmitting, with the firstcommunication device and after transmission of the beamforming trainingpacket by the first communication device, the trigger frame to the atleast some of the multiple communication devices. The methodadditionally includes receiving, at the first communication device, theuplink OFDMA transmission, wherein the uplink OFDMA transmissionincludes respective beamforming training feedback packets generatedbased on the beamforming training packet by respective ones of the atleast some of the multiple second communication devices, and wherein therespective beamforming training feedback packets are simultaneouslytransmitted by the at least some of the multiple second communicationdevices.

In another embodiment, an apparatus comprises a network interface devicehaving one or more integrated circuits configured to transmit abeamforming training packet to multiple communication devices. The oneor more integrated circuits are also configured to generate a triggerframe to trigger an uplink orthogonal frequency division multiple access(OFDMA) transmission of beamforming training feedback from at least someof the multiple communication devices. The one or more integratedcircuits are further configured to, after transmission of thebeamforming training, transmit the trigger frame to the at least some ofthe multiple communication devices. The one or more integrated circuitsare additionally configured to receive the uplink OFDMA transmission,wherein the uplink OFDMA transmission includes respective beamformingtraining feedback packets generated based on the beamforming trainingpacket by respective ones of the at least some of the multiplecommunication devices, and wherein the respective beamforming trainingfeedback packets are simultaneously transmitted by the at least some ofthe multiple communication devices.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram of an example wireless local area network(WLAN), according to an embodiment.

FIG. 2 is a diagram of an example transmission sequence in a WLAN,according to an embodiment;

FIG. 3 is a diagram of an example transmission sequence in a WLAN,according to another embodiment;

FIG. 4 is a diagram of an example transmission sequence in a WLAN,according to another embodiment;

FIG. 5A is a diagram of an announcement frame, according to anembodiment;

FIG. 5B is a diagram of a frame body of an announcement frame, accordingto an embodiment;

FIG. 5C is a diagram of per-station (per-STA) information fields of anannouncement frame, according to an embodiment;

FIG. 5D is a diagram of a per-STA information field, according to anembodiment; and

FIG. 6 is a flow diagram of an example method for beamforming trainingin a WLAN, according to an embodiment.

DETAILED DESCRIPTION

In embodiments described below, a wireless network device such as anaccess point (AP) of a wireless local area network (WLAN) simultaneouslytransmits data to multiple client stations and/or receives datasimultaneously transmitted by multiple client stations. In someembodiments, the AP transmits data for the multiple clients in differentorthogonal frequency division multiplexing (OFDM) sub-channels of anorthogonal frequency division multiple access (OFDMA) transmission.Similarly, multiple client stations simultaneously transmit data to theAP, in particular, each client station transmits data in a differentOFDM sub-channel of an OFDMA transmission, in an embodiment. The AP isconfigured to beamform or steer transmissions to client stations, usingchannel information obtained from the client stations, in someembodiments. For example, according to an embodiment, the AP implementsan explicit beamforming technique in which the AP transmits abeamforming training packet, or a sounding packet, that allows each ofthe multiple client stations to determine or estimate characteristics ofthe channel (channel information) between the AP and the client station.In an embodiment, the AP also transmits a trigger frame to triggermultiple client stations to simultaneously (e.g., in respectivefrequency portions) transmit feedback that includes channel information,or steering information (e.g., a steering matrix) determined based onthe channel information, to the AP. The AP transmits the trigger frameafter transmitting the beamforming training packet, in an embodiment.Transmitting the trigger frame after transmitting the beamformingtraining packet ensures that the client stations will have sufficientamount of time to obtain channel information and to generate feedbackbased on the channel information before the feedback is to betransmitted by the client stations to the AP, in an embodiment.

The AP is configured to operate with client stations according to atleast a first communication protocol. The first communication protocolis sometimes referred to herein as “high efficiency,” “high efficiencyWiFi,” “high efficiency WLAN,” “HE,” “HEW,” or 802.11ax communicationprotocol. The first communication protocol supports OFDMA communicationbetween the AP and the client stations. In some embodiments, differentclient stations in the vicinity of the AP are configured to operateaccording to one or more other communication protocols that defineoperation in the same frequency band as the HE communication protocolbut with generally lower data throughputs. The lower data throughputcommunication protocols (e.g., IEEE 802.11a, IEEE 802.11n, and/or IEEE802.11ac) are collectively referred herein as “legacy” communicationprotocols. The legacy communication protocols do not support OFDMAcommunication, in an embodiment.

FIG. 1 is a block diagram of an example wireless local area network(WLAN) 10, according to an embodiment. An AP 14 includes a hostprocessor 15 coupled to a network interface 16. In an embodiment, thenetwork interface 16 includes one or more integrate circuits (ICs)configured to operate as discussed below. The network interface 16includes a medium access control (MAC) processor 18 and a physical layer(PHY) processor 20. The PHY processor 20 includes a plurality oftransceivers 21, and the transceivers 21 are coupled to a plurality ofantennas 24. Although three transceivers 21 and three antennas 24 areillustrated in FIG. 1, the AP 14 includes other suitable numbers (e.g.,1, 2, 4, 5, etc.) of transceivers 21 and antennas 24 in otherembodiments. In some embodiments, the AP 14 includes a higher number ofantennas 24 than transceivers 21, and antenna switching techniques areutilized. In an embodiment, the MAC processor 18 is implemented on atleast a first IC, and the PHY processor 20 is implemented on at least asecond IC. In an embodiment, at least a portion of the MAC processor 18and at least a portion of the PHY processor 20 are implemented on asingle IC.

In various embodiments, the MAC processor 18 and the PHY processor 20are configured to operate according to a first communication protocol(e.g., a High Efficiency, HE, or 802.11ax communication protocol). Insome embodiments, the MAC processor 18 and the PHY processor 20 are alsoconfigured to operate according to a second communication protocol(e.g., according to the IEEE 802.11ac Standard). In yet anotherembodiment, the MAC processor 18 and the PHY processor 20 areadditionally configured to operate according to the second communicationprotocol, a third communication protocol, and/or a fourth communicationprotocol (e.g., according to the IEEE 802.11a Standard and/or the IEEE802.11n Standard).

The WLAN 10 includes a plurality of client stations 25. Although fourclient stations 25 are illustrated in FIG. 1, the WLAN 10 includes othersuitable numbers (e.g., 1, 2, 3, 5, 6, etc.) of client stations 25 invarious scenarios and embodiments. At least one of the client stations25 (e.g., client station 25-1) is configured to operate at leastaccording to the first communication protocol. In some embodiments, atleast one of the client stations 25 is not configured to operateaccording to the first communication protocol but is configured tooperate according to at least one of the second communication protocol,the third communication protocol, and/or the fourth communicationprotocol (referred to herein as a “legacy client station”).

The client station 25-1 includes a host processor 26 coupled to anetwork interface 27. In an embodiment, the network interface 27includes one or more ICs configured to operate as discussed below. Thenetwork interface 27 includes a MAC processor 28 and a PHY processor 29.The PHY processor 29 includes a plurality of transceivers 30, and thetransceivers 30 are coupled to a plurality of antennas 34. Althoughthree transceivers 30 and three antennas 34 are illustrated in FIG. 1,the client station 25-1 includes other suitable numbers (e.g., 1, 2, 4,5, etc.) of transceivers 30 and antennas 34 in other embodiments. Insome embodiments, the client station 25-1 includes a higher number ofantennas 34 than transceivers 30, and antenna switching techniques areutilized. In an embodiment, the MAC processor 28 is implemented on atleast a first IC, and the PHY processor 29 is implemented on at least asecond IC. In an embodiment, at least a portion of the MAC processor 28and at least a portion of the PHY processor 29 are implemented on asingle IC.

According to an embodiment, the client station 25-4 is a legacy clientstation, i.e., the client station 25-4 is not enabled to receive andfully decode a data unit that is transmitted by the AP 14 or anotherclient station 25 according to the first communication protocol.Similarly, according to an embodiment, the legacy client station 25-4 isnot enabled to transmit data units according to the first communicationprotocol. On the other hand, the legacy client station 25-4 is enabledto receive and fully decode and transmit data units according to thesecond communication protocol, the third communication protocol, and/orthe fourth communication protocol.

In an embodiment, one or both of the client stations 25-2 and 25-3, hasa structure that is the same as or similar to the client station 25-1.In an embodiment, the client station 25-4 has a structure similar to theclient station 25-1. In these embodiments, the client stations 25structured the same as or similar to the client station 25-1 have thesame or a different number of transceivers and antennas. For example,the client station 25-2 has only two transceivers and two antennas (notshown), according to an embodiment.

In various embodiments, the MAC processor 18 and the PHY processor 20 ofthe AP 14 are configured to generate data units conforming to the firstcommunication protocol and having formats described herein. In anembodiment, the MAC processor 18 is configured to implement MAC layerfunctions, including MAC layer functions of the first communicationprotocol. In an embodiment, the PHY processor 20 is configured toimplement PHY functions, including PHY functions of the firstcommunication protocol. For example, in an embodiment, the MAC processor18 is configured to generate MAC layer data units such as MPDUs, MACcontrol frames, etc., and provide the MAC layer data units to the PHYprocessor 20. In an embodiment, the PHY processor 20 is configured toreceive MAC layer data units from the MAC processor 18 and encapsulatethe MAC layer data units to generate PHY data units such as PHY protocoldata units (PPDUs) for transmission via the antennas 24. Similarly, inan embodiment, the PHY processor 20 is configured to receive PHY dataunits that were received via the antennas 24, and extract MAC layer dataunits encapsulated within the PHY data units. In an embodiment, the PHYprocessor 20 provides the extracted MAC layer data units to the MACprocessor 18, which processes the MAC layer data units.

The transceiver(s) 21 is/are configured to transmit the generated dataunits via the antenna(s) 24. Similarly, the transceiver(s) 21 is/areconfigured to receive data units via the antenna(s) 24. The MACprocessor 18 and the PHY processor 20 of the AP 14 are configured toprocess received data units conforming to the first communicationprotocol and having formats described hereinafter and to determine thatsuch data units conform to the first communication protocol, accordingto various embodiments.

In various embodiments, the MAC processor 28 and the PHY processor 29 ofthe client device 25-1 are configured to generate data units conformingto the first communication protocol and having formats described herein.In an embodiment, the MAC processor 28 is configured to implement MAClayer functions, including MAC layer functions of the firstcommunication protocol. In an embodiment, the PHY processor 29 isconfigured to implement PHY functions, including PHY functions of thefirst communication protocol. For example, in an embodiment, the MACprocessor 28 is configured to generate MAC layer data units such asMPDUs, MAC control frames, etc., and provide the MAC layer data units tothe PHY processor 29. In an embodiment, the PHY processor 29 isconfigured to receive MAC layer data units from the MAC processor 28 andencapsulate the MAC layer data units to generate PHY data units such asPPDUs for transmission via the antennas 34. Similarly, in an embodiment,the PHY processor 29 is configured to receive PHY data units that werereceived via the antennas 34, and extract MAC layer data unitsencapsulated within the PHY data units. In an embodiment, the PHYprocessor 29 provides the extracted MAC layer data units to the MACprocessor 28, which processes the MAC layer data units.

The transceiver(s) 30 is/are configured to transmit the generated dataunits via the antenna(s) 34. Similarly, the transceiver(s) 30 is/areconfigured to receive data units via the antenna(s) 34. The MACprocessor 28 and the PHY processor 29 of the client device 25-1 areconfigured to process received data units conforming to the firstcommunication protocol and having formats described hereinafter and todetermine that such data units conform to the first communicationprotocol, according to various embodiments.

FIG. 2 is a diagram of an example transmission sequence 200 in a WLAN,such as the WLAN 10 of FIG. 1, according to an embodiment, in which anAP, such as the AP 14, performs beamforming training with multipleclient stations, such as multiple ones of the client stations 25. The AP14 transmits an announcement frame 202 to multiple client stations 25.The announcement frame 202 is a downlink (DL) frame because theannouncement frame 204 is transmitted in the downlink direction from theAP 14 to the client stations 25, in an embodiment. In an embodiment, theannouncement frame 202 identifies client stations 25 that are toparticipate in the beamforming training. For example, the announcementframe 204 includes a respective identifier, such as an associationidentifier (AID) or a partial AID (PAID), associated with each clientstation 25 that is an intended participant of the beamforming training,in an embodiment. In an embodiment, the announcement frame 202 is a nulldata packet announcement (NDPA) frame. In an embodiment, theannouncement frame 202 is a broadcast control frame that occupies theentire bandwidth of the communication channel in which the beamformingtraining is being performed. Thus, for example, in an embodiment inwhich the beamforming training is being performed in an 80 MHz-widecommunication channel, the announcement frame 202 occupies an 80 MHzbandwidth. As another example, in an embodiment in which the beamformingtraining is being performed in a 40 MHz-wide communication channel, theannouncement frame 202 occupies a 40 MHz bandwidth. In anotherembodiment, in which the beamforming training is being performed in acommunication channel of another suitable width, the announcement frame202 occupies a corresponding bandwidth of the other suitable width.

After transmitting the announcement frame 202, the AP 14 transmits abeamforming training packet 204, such as a null data packet (NDP), tosound the communication channel. The beamforming training packet 204 isa DL packet, in an embodiment. The beamforming training packet 204occupies the bandwidth of the communication channel in which thebeamforming training is being performed (i.e., the communication channelbeing sounded), in an embodiment. The beamforming training packet 204includes one or more training signals, such as one or more trainingfields (e.g., long training fields (LTFs)), that allow each of themultiple client stations 25 to estimate the channel between the AP 14and the client station 25, in an embodiment. In an embodiment, the AP 14initiates transmission of the beamforming training packet 204 uponexpiration of a predetermined time interval after the end oftransmission of the announcement frame 202. In an embodiment, thepredetermined time interval is a time interval corresponding to a shortinter-frame space (SIFS) defined by the first communication protocol(e.g., IEEE 802.11ax) and/or by a legacy communication protocol (e.g.,the IEEE 802.11n/ac). In another embodiment, the predetermined timeinterval is a suitable time interval different from SIFS time interval.In another embodiment, the predetermined time interval is a suitabletime interval different from a SIFS time interval.

After transmitting the beamforming training packet 204, the AP 14transmits a trigger frame 206 to trigger transmission of beamformingfeedback from at least some of the multiple client stations 25, whichare participating in the beamforming training, to the AP 14. The triggerframe 206 is a DL frame, in an embodiment. In an embodiment, the AP 14initiates transmission of the trigger frame 206 upon expiration of apredetermined time interval after the end of transmission of thebeamforming training packet 204. In an embodiment, the predeterminedtime interval is a time interval corresponding to the SIFS time intervaldefined by the first communication protocol (e.g., IEEE 802.11ax) and/orby a legacy communication protocol (e.g., the IEEE 802.11n/ac). Inanother embodiment, the predetermined time interval is a suitable timeinterval different from a SIFS time interval. In an embodiment, thetrigger frame 206 triggers the at least some of the multiple clientstations 25 to transmit respective feedback packets simultaneously,using different frequency portions of an uplink OFDMA transmission fromthe at least some of the client stations 25 to the AP 14. The triggerframe 206 includes one or more fields for specifying one or more of i) atrigger type (e.g., that the trigger frame 206 is a beamforming trigger,ii) one or more PHY parameters that are to be utilized for transmissionof feedback, iv) resource unit allocations indicating which frequencyportions correspond with which client stations, etc., according tovarious embodiments. The trigger frame 206 has a suitable format, suchas a format described in U.S. patent application Ser. No. 14/961,380(Attorney Docket No. MP6128) and/or U.S. patent application Ser. No.14/961,635 (Attorney Docket No. MP6558), or another suitable format,according to various embodiments.

In response to receiving the trigger frame 206, the at least some of themultiple client stations 25 triggered by the trigger frame 206 transmitbeamforming feedback (e.g., feedback packets) in an OFDMA transmission208 to the AP 14. The OFDMA transmission 208 is an uplink (UL)transmission because OFDMA transmission 208 is transmitted in the uplinkdirection from the client stations 25 to the AP 14, in an embodiment. Inan embodiment, each client station 25 initiates transmission of thefeedback (e.g., a feedback packet) upon expiration of a predeterminedtime interval, such as, for example, a time interval corresponding toSIFS, after completion of reception of the trigger frame 206. Because,in the transmission sequence 200, the beamforming training packet 204 istransmitted by the AP 14 before the trigger frame 206 is transmitted bythe AP 14, the client stations 25 have sufficient amount of time toperform channel estimation based on the beamforming training packet 204,and to generate the feedback based on the channel estimation, in anembodiment. Accordingly, transmission of the feedback packets by theclient stations 25 as parts of the uplink OFDMA transmission 208 canbegin upon expiration of a relatively short time interval after the endof reception of the trigger frame 204 by the client stations 25, such asthe time interval corresponding to SIFS, in an embodiment.

FIG. 3 is a diagram of an example transmission sequence 300 in a WLAN,such as the WLAN 10 of FIG. 1, according to an embodiment, in which anAP, such as the AP 14, performs beamforming training with multipleclient stations, such as multiple ones of the client stations 25. Thetransmission sequence 300 is similar to the transmission sequence 200 ofFIG. 2 except that the announcement frame 202 in the transmissionsequence 200 is replaced with an announcement frame 302. Unlike theannouncement frame 202 which occupies an entire bandwidth of the channelin which the beamforming training is being performed, the announcementframe 302 is a duplicate frame that is duplicated in each of a pluralityof subchannels of the channel in which the beamforming training is beingperformed. Thus, for example, in an embodiment in which the beamformingtraining is being performed in an 80 MHz-wide communication channel, theannouncement frame 202 is duplicated in each of four 20 MHz-widesubchannels of the 80 MHz-wide communication channel, in an embodiment.As another example, in an embodiment in which the beamforming trainingis being performed in a 40 MHz-wide communication channel, theannouncement frame 202 is duplicated in each of two 20 MHz-widesubchannels of the 40 MHz-wide communication channel, in an embodiment.The announcement frame 202 is duplicated in another suitable number ofsubchannels of the communication channel in which the beamformingtraining is being performed, in another embodiment.

In an embodiment, the announcement frame 302 has a format the same as orsimilar to a beamforming announcement frame defined by a legacycommunication protocol, such as the IEEE 802-11n/ac Standard. In anembodiment, a legacy communication device is configured to receive,decode, and at least partially understand information included in theannouncement frame 302. Such format of the announcement frame 302 allowsone or more legacy client stations, such as the legacy client station25-4, along with one or more non-legacy client stations, such as theclient stations 25-1, 25-2, 15-3, to participate in the beamformingtraining, in an embodiment. In an embodiment, however, such format ofthe announcement frame 302 is used even when the plurality of clientstations that are intended participants of the beamforming trainingbeing announced by the announcement frame does not include any legacyclient stations.

FIG. 4 is a diagram of an example transmission sequence 400 in a WLAN,such as the WLAN 10 of FIG. 1, according to an embodiment, in which anAP, such as the AP 14, performs beamforming training with multipleclient stations, such as multiple ones of the client stations 25. Thetransmission sequence 400 is similar to the transmission sequence 300 ofFIG. 3, except that the transmission sequence 400 includes transmissionof feedback by a legacy client station, such as the legacy clientstation 25-4, in an embodiment. For example, the multiple clientstations 25 that are participating in the beamforming training include alegacy client station that is not configured to operate according to thefirst communication protocol, in an embodiment. The legacy clientstation is not configured for OFDMA communication, in an embodiment.

In an embodiment, in the scenario illustrated in FIG. 4, theannouncement frame 302 identifies the legacy client station among themultiple client stations that are intended participants in thebeamforming training being announced by the announcement frame 302. Thelegacy client station is able to receive and decode the announcementframe 302 and to determine, based on the announcement frame 302, thatthe legacy client station is to participate in the beamforming trainingbeing announced by the announcement frame 302, in an embodiment. Thelegacy client station then receives the beamforming training packet 204,transmitted by the AP 14 to the multiple of client stations 25 thatinclude the legacy client station, and generates feedback based on thebeamforming training packet 204, in an embodiment.

The trigger frame 206 triggers at least some of the non-legacy clientstations to transmit feedback from at least some of non-legacy clientstations 25 of the plurality of client stations 25 that areparticipating in the beamforming training announced by the announcementframe 302, in an embodiment. After receiving the uplink OFDMAtransmission 208 that includes respective feedback packets from the atleast some of the non-legacy client stations 25 triggered by the triggerframe 302, the AP 14 transmits a poll frame 410. The poll frame 410 is aduplicate frame that is duplicated in each of a plurality of subchannelsof the communication channel in which the beamforming training is beingperformed, in an embodiment. In an embodiment, the poll frame 410 has abeamforming feedback poll frame format defined by the legacycommunication protocol according to which the legacy client station isconfigured to operate, such the IEEE 802.11n/ac Standard. In anembodiment, the AP 14 initiates transmission of the poll frame 410 uponexpiration of a predetermined time interval, such as for example a timeinterval corresponding to SIFS, after completion of reception of theOFDMA transmission 208.

In response to receiving the poll frame 410, the legacy client stationtransmits a feedback packet 412 to the AP 14. In an embodiment, if morethan one client legacy station is participating in the beamformingtraining, the AP 14 transmits additional poll frames after receiving theBF feedback 412 from the legacy client station polled by the poll frame410. Thus, for example, the transmission sequence 400 includes one ormore additional frame exchanges 410, 412 via which the AP 14 obtainsfeedback from one or more additional In an embodiment, the one or moreadditional poll frames transmitted by the AP 14 trigger, one by one,trigger additional legacy client station(s) to transmit feedback packetsto the AP 14 as defined by the by the legacy communication protocolaccording to which the legacy client stations are configured to operate,such the IEEE 802.11n/ac Standard.

FIG. 5A is a block diagram of an announcement frame 500, according to anembodiment. In an embodiment, the announcement frame 500 corresponds tothe announcement frame 202 of FIG. 2 or the announcement frame 302 ofFIGS. 3 and 4. The announcement frame 500 includes a plurality offields, including a frame control field 502, a duration/ID field 504, afirst address field (e.g., a receiver address (RA) field) 506, a secondaddress field (e.g., a transmitter address (TA) field) 508, a frame bodyfield 510 and a frame check field 512.

In an embodiment, the duration/ID field 504 includes an indication of aduration until the end of a transmission opportunity (TXOP) for thebeamforming training initiated by the announcement frame 500. The firstaddress field (RA field) 506 includes a broadcast MAC address toindicate that the announcement frame 500 is being broadcast to aplurality of client stations 25, in an embodiment. The second addressfield (TA field) 508 includes the address of the AP 14, in anembodiment. In an embodiment, the frame body 510 includes identifiesclient station 25 that are to participate in the beamforming trainingprocedure, and also indicates beamforming control information to theidentified client statins 25. Referring to FIG. 5B, in an embodiment,the frame body 510 includes a sounding token field 520 and per-STAinformation fields 522. The frame body 510 also includes padding bits524, in some embodiments and scenarios. In an embodiment, padding bits524 include one or more bits to ensure that the frame body 510 includesa number of bits that is an integer multiple of an octet. In anotherembodiment, padding bits 524 include one or more bits to providesufficient time for a receiving device (e.g., a client station) togenerate the uplink transmission being triggered by the trigger frame500. In some embodiments and/or scenarios, the frame body 510 omits thepadding bits 524.

FIG. 5C is a diagram of the per-STA information fields 522, according toan embodiment. The per-STA information fields 522 includes a pluralityof subfields 530, each subfield 530 corresponding to a particular clientstation or to a particular client station 25, in an embodiment. Asillustrated in FIG. 5D, each per-STA information field 530 includes anSTAID subfield 532 and a feedback control information subfield 534. Inan embodiment, the STAID subfield 532 identifies a particular clientstation 25 that is an intended participant in the beamforming trainingprocedure. In an embodiment, the STAID subfield 532 is the same as orsimilar to the STAID subfield 702-4 described above with respect to FIG.7A. The feedback control information subfield 534 indicates feedbackinformation such as a feedback type, a beamforming bandwidth (e.g., abandwidth of the beamforming training packet that follows theannouncement frame 500), an Nc index that indicates a number of columnsin a feedback matrix to be provided by the corresponding client station25 to the AP 14, etc., in an embodiment.

In an embodiment in which a legacy client station is a participant inthe beamforming training, such as the embodiment described above withreference to FIG. 4, the legacy client station is configured toautomatically transmit feedback after reception of a beamformingtraining packet, such as the beamforming training packet 204, if thelegacy client station is identified by the per-STA information subfield530-2 corresponding to STA0. For example, the legacy communicationprotocol according to which the legacy client station is configured tooperate specifies that the client station that is identified as STA0 ina beamforming announcement frame should automatically transmit itsfeedback upon expiration of a predetermined time interval (e.g., SIFS)after reception of a beamforming training packet that follows thebeamforming announcement frame, in an embodiment. In an embodiment, theAP 14 is configured to suppress automatic transmission of feedback bythe legacy client station to avoid collision of the feedback with thetrigger frame 206. For example, the AP 14 is configured to set theper-STA information subfield 530-2 corresponding to STA0 to a reservedvalue (e.g., 0), or a value of an STAID that is not associated with anyclient station 25 in the WLAN 10, in an embodiment.

FIG. 6 is a flow diagram of an example method 600 for beamformingtraining in a wireless communication network, according to anembodiment. In some embodiments, the method 600 is implemented by the AP14 (FIG. 1). For example, in some embodiments, the network interfacedevice 16 (e.g., the PHY processor 20 and/or the MAC processor 18) isconfigured to implement the method 600. In other embodiments, anothersuitable network interface device is configured to implement the method600.

At block 602, a beamforming training packet is transmitted to multiplecommunication devices. In an embodiment, the beamforming training packet204 of FIGS. 2, 3, 4 is transmitted. In another embodiment, anothersuitable beamforming training packet is transmitted. In an embodiment,the beamforming training packet includes one or more training fieldsthat allow the multiple communication devices to obtain measures ofrespective communication channels associated with the communicationdevices.

At block 604, a trigger frame is generated. In an embodiment, thetrigger frame 206 of FIGS. 2, 3, 4, is generated. In another embodiment,another suitable trigger frame is generated. In an embodiment, thetrigger frame is generated to trigger an uplink OFDMA transmission fromat least some of the multiple communication devices. In an embodiment,the trigger frame includes information to indicate respective frequencyportions of the uplink OFDMA transmission, the respective frequencyportions corresponding with respective ones of the at least some of themultiple communication devices.

At block 606, after the beamforming training packet is transmitted atblock 602, the trigger frame generated at block 606 is transmitted tothe at least some of the multiple communication devices.

At block 608, the uplink OFDMA transmission is received. In anembodiment, the uplink OFDMA transmission includes respectivebeamforming training feedback packets from respective ones of the atleast some of the multiple communication devices. In an embodiment, therespective beamforming training feedback packets are simultaneouslytransmitted by the at least some of the multiple communication devices.In an embodiment, the respective beamforming feedback packets aretransmitted, by the at least some of the multiple communication device,in the respective frequency portions corresponding with the at leastsome of the multiple communication devices.

In an embodiment, each of the multiple communication devices receivesthe beamforming training packet transmitted at block 602, and generatesbeamforming feedback based on the received beamforming training packet.Each of the at least some of the multiple communication devices beingtriggered by the trigger frame transmitted at block 606 receives thetrigger frame and determines, based on the received trigger frame, thatthe communication device is being triggered to transmit the feedbackgenerated based on the beamforming training packet transmitted at block602, in an embodiment. In response to receiving the trigger frame, eachof the at least some of the multiple communication devices transmits thefeedback generated based on the beamforming training packet transmittedat block 602, in an embodiment. In an embodiment, because the triggerframe is transmitted at block 606 after the beamforming training packetis transmitted at block 602, each of the at least some multiplecommunication devices that is to transmit the feedback in response toreceiving the trigger frame at block 606 has sufficient amount of timeto generate the feedback based on the beamforming training packettransmitted at block 602 and to transmit the feedback upon expiration ofa relatively short time interval after receiving the trigger frametransmitted at block 606. For example, each of the at least some of themultiple communication devices transmits the feedback upon expiration ofa time interval corresponding to SIFS after receiving the trigger frame,in an embodiment.

In an embodiment, a method for beamforming training in a wirelesscommunication network includes transmitting, from a first communicationdevice, a beamforming training packet to multiple second communicationdevices. The method also includes generating, at the first communicationdevice, a trigger frame to trigger an uplink orthogonal frequencydivision multiple access (OFDMA) transmission of beamforming trainingfeedback from at least some of the multiple second communicationdevices. The method further includes transmitting, with the firstcommunication device and after transmission of the beamforming trainingpacket by the first communication device, the trigger frame to the atleast some of the multiple communication devices. The methodadditionally includes receiving, at the first communication device, theuplink OFDMA transmission, wherein the uplink OFDMA transmissionincludes respective beamforming training feedback packets generatedbased on the beamforming training packet by respective ones of the atleast some of the multiple second communication devices, and wherein therespective beamforming training feedback packets are simultaneouslytransmitted by the at least some of the multiple second communicationdevices.

In other embodiments, the method includes any suitable combination ofone or more of the following features.

Transmitting the trigger frame comprises transmitting the trigger frameupon expiration of a first predetermined time interval aftertransmission of the beamforming training packet.

The first predetermined time interval corresponds to a short inter-framespacing (SIFS) time interval.

The trigger frame causes the second communication devices to transmitthe respective beamforming training feedback packets upon expiration ofa second predetermined time interval after reception of the triggerframe by the second communication devices.

The second predetermined time interval corresponds to a shortinter-frame spacing (SIFS) time interval.

The trigger frame includes information to indicate respective frequencyportions of the uplink OFDMA transmission, the respective frequencyportions corresponding with respective ones of the at least some of themultiple second communication devices.

The respective beamforming training feedback packets simultaneouslytransmitted by the least some of the multiple second communicationdevices are transmitted in the respective frequency portionscorresponding with the at least some of the multiple secondcommunication devices.

The method further comprises, prior to transmitting the beamformingpacket, transmitting, with the first communication device, anannouncement frame to the multiple second communication devices, whereinthe announcement frame identifies the multiple second communicationdevices.

The announcement frame occupies an entire bandwidth of the communicationchannel.

The announcement frame is duplicated in each of a plurality ofsubchannels of the communication channel.

The multiple second communication devices include a legacy communicationdevice that is not configured for OFDMA communication.

The method further comprises, after receiving the uplink OFDMAtransmission, transmitting a polling frame to trigger transmission offeedback from the legacy communication device.

The method further comprises including, in the announcement frame, anindication to suppress automatic feedback by the legacy secondcommunication device.

In another embodiment, an apparatus comprises a network interface devicehaving one or more integrated circuits configured to transmit abeamforming training packet to multiple communication devices. The oneor more integrated circuits are also configured to generate a triggerframe to trigger an uplink orthogonal frequency division multiple access(OFDMA) transmission of beamforming training feedback from at least someof the multiple communication devices. The one or more integratedcircuits are further configured to, after transmission of thebeamforming training, transmit the trigger frame to the at least some ofthe multiple communication devices. The one or more integrated circuitsare additionally configured to receive the uplink OFDMA transmission,wherein the uplink OFDMA transmission includes respective beamformingtraining feedback packets generated based on the beamforming trainingpacket by respective ones of the at least some of the multiplecommunication devices, and wherein the respective beamforming trainingfeedback packets are simultaneously transmitted by the at least some ofthe multiple communication devices.

In other embodiments, the apparatus includes any suitable combination ofone or more of the following features.

The one or more integrated circuits are configured to transmit thetrigger frame upon expiration of a first predetermined time intervalafter transmission of the beamforming training packet.

The first predetermined time interval corresponds to a short inter-framespacing (SIFS) time interval.

The trigger frame causes the second communication devices to transmitthe respective beamforming training feedback packets upon expiration ofa second predetermined time interval after reception of the triggerframe by the multiple communication devices.

The second predetermined time interval corresponds to a shortinter-frame spacing (SIFS) time interval.

The trigger frame includes information to indicate respective frequencyportions of the uplink OFDMA transmission, the respective frequencyportions corresponding with respective ones of the at least some of themultiple communication devices.

The respective beamforming training feedback packets simultaneouslytransmitted by the least some of the multiple communication devices aretransmitted in the respective frequency portions corresponding with theat least some of the multiple communication devices.

The one or more integrated circuits are further configured to, prior totransmitting the beamforming packet, transmit an announcement frame tothe multiple communication devices, wherein the announcement frameidentifies the multiple communication devices.

The announcement frame occupies an entire bandwidth of the communicationchannel.

The announcement frame is duplicated in each of a plurality ofsubchannels of the communication channel.

The multiple communication devices include a legacy communication devicethat is not configured for OFDMA communication, and wherein the methodfurther comprises, after receiving the uplink OFDMA transmission,transmitting a polling frame to trigger transmission of feedback fromthe legacy communication device.

The one or more integrated circuits are further configured to include inthe announcement frame an indication to suppress automatic feedback bythe legacy second communication device.

At least some of the various blocks, operations, and techniquesdescribed above may be implemented utilizing hardware, a processorexecuting firmware instructions, a processor executing softwareinstructions, or any combination thereof. When implemented utilizing aprocessor executing software or firmware instructions, the software orfirmware instructions may be stored in any computer readable memory suchas on a magnetic disk, an optical disk, or other storage medium, in aRAM or ROM or flash memory, processor, hard disk drive, optical diskdrive, tape drive, etc. The software or firmware instructions mayinclude machine readable instructions that, when executed by one or moreprocessors, cause the one or more processors to perform various acts.

When implemented in hardware, the hardware may comprise one or more ofdiscrete components, an integrated circuit, an application-specificintegrated circuit (ASIC), a programmable logic device (PLD), etc.

While the present invention has been described with reference tospecific examples, which are intended to be illustrative only and not tobe limiting of the invention, changes, additions and/or deletions may bemade to the disclosed embodiments without departing from the scope ofthe invention.

What is claimed is:
 1. A method for beamforming training in a wirelesscommunication network, the method comprising: transmitting, from a firstcommunication device, a transmission to multiple second communicationdevices, wherein the transmission indicates that the first communicationdevice will subsequently transmit a null data packet (NDP), wherein themultiple second communication devices include i) a plurality ofnon-legacy second communication devices and ii) a legacy secondcommunication device, wherein the transmission includes an NDPannouncement frame that includes multiple per-station information fieldsfor indicating respective second communication devices that are toprovide feedback in response to the NDP, wherein the multipleper-station information fields are arranged in an order, wherein afirst-occurring per-station information field in the order is set toindicate an address that has not been allocated to any communicationdevices in the wireless communication network, and wherein anotherper-station information field after the first-occurring per-stationinformation field is set to indicate an address of the legacy secondcommunication device; transmitting, from the first communication device,the NDP; generating, at the first communication device, a trigger frameto trigger an uplink orthogonal frequency division multiple access(OFDMA) transmission of beamforming training feedback from at least somenon-legacy second communication devices among the plurality ofnon-legacy second communication devices; transmitting, with the firstcommunication device and after transmission of the NDP by the firstcommunication device, the trigger frame to the at least some non-legacysecond communication devices among the plurality of non-legacy secondcommunication devices; receiving, at the first communication device, theuplink OFDMA transmission, wherein the uplink OFDMA transmissionincludes respective beamforming training feedback packets generatedbased on the NDP by respective ones of the at least some non-legacysecond communication devices among the plurality of non-legacy secondcommunication devices, and wherein the respective beamforming trainingfeedback packets are simultaneously transmitted by the at least somenon-legacy second communication devices among the plurality ofnon-legacy second communication devices; and after receiving the uplinkOFDMA transmission, transmitting a polling frame to trigger transmissionof beamforming training feedback, corresponding to the NDP, from thelegacy second communication device.